1. Field of the Invention
The present invention relates to a method and apparatus for drying a wafer and an apparatus for cleaning and drying a wafer. More particularly, the present invention relates to a method and apparatus for drying a wafer using an isopropyl alcohol vapor and an apparatus for cleaning using a cleaning solution and then drying the cleaned wafer using an isopropyl alcohol gas.
2. Description of the Related Art
Generally, a semiconductor device is manufactured by a fabrication process for forming an electrical circuit on a silicon substrate that is used for a semiconductor substrate, an electrical die sorting (EDS) process for testing electrical characteristics of the electric circuit, and a packaging process for enclosing the substrate with an epoxy resin and then separating the substrate into single chips.
The fabrication process includes a deposition process for forming a layer on a wafer, a chemical mechanical polishing process for planarizing a surface of the layer, a photolithography process for forming a photoresist pattern on the layer, an etching process for forming a pattern having electrical characteristics using the photoresist pattern as an etching mask, an implantation process for implanting ions into predetermined regions of the wafer, a cleaning process for removing particles from a surface of the wafer, a drying process for drying the wafer after the cleaning process, and a testing process for detecting defects of the layer or the pattern.
In the cleaning process, the wafer is dipped into a cleaning solution or a rinsing solution to remove particles from the surface of the wafer. An apparatus for cleaning a wafer, capable of carrying out the above-described cleaning process, is provided with an apparatus for drying a wafer. The apparatus for drying a wafer removes moisture from the wafer using the Marangoni effect. In particular, a drying gas including a volatile organic solution gas, such as an isopropyl alcohol gas, is provided to the rinsing solution remaining on the surface of the wafer to remove the moisture from the wafer.
An apparatus for cleaning and drying a wafer is disclosed in U.S. Pat. No. 6,068,002 issued to Kamikawa, the apparatus of which includes a cleaning tank for storing a cleaning solution or a rinsing solution, a drying tank disposed over the cleaning tank, a shutter disposed between the cleaning tank and drying tank, and a wafer boat for transferring the wafer between the cleaning tank and drying tank.
The wafer boat supports a plurality of wafers. The wafers are inserted into slots of the wafer boat in a vertical direction. A pair of nozzles is disposed on both inner sides of the drying chamber. The nozzles spray the drying gas including an isopropyl alcohol gas on an upper portion of the wafer. The isopropyl alcohol gas removes the moisture from the wafer.
FIG. 1 is a schematic cross-sectional view illustrating a conventional apparatus 100 for drying a wafer or wafers. Referring to FIG. 1, the conventional apparatus 100 for drying a wafer includes a drying tank 110, a drying gas supply unit 120, a pair of nozzles 136 and a wafer boat 140.
The drying tank 110 defining a drying chamber 110a is disposed over a cleaning tank (not shown). A shutter 150, which moves horizontally, is disposed between the cleaning tank and the drying tank 110. The shutter 150 operates to separate the cleaning tank and the drying tank 110 from each other. The drying tank 110 includes a fixed base 112 and a top cover 114. The fixed base 112 is disposed on the cleaning tank. The top cover 114 having an arch-shaped section moves in a direction substantially perpendicular to the fixed base 112. Sealing members 160 are interposed between the fixed base 112 and the top cover 114 and between the fixed base 112 and shutter 150, respectively.
The wafer boat 140 in which a plurality of wafers W, for example 50 wafers, is received in a line, is disposed in the drying tank 110. The wafer boat 140 transfers the wafers W between the cleaning tank and the drying tank 110. The wafer boat 140 includes a plurality of slots for holding the wafers W. Each wafer is inserted into one of the slots of the wafer boat 140 and is aligned vertically.
The pair of nozzles 136 is disposed in the drying tank 110. In detail, the nozzles 136 are disposed adjacent to both sides of the fixed base 112. The nozzles 136 provide a drying gas into the drying tank 110.
The nozzles 136 are connected to the drying gas supply unit 120. The nozzles 136 spray the drying gas relatively toward an upper portion of the aligned wafers. After the nozzles 136 spray the drying gas upwardly, the drying gas flows upwardly from the nozzles 136 along the inner sidewall of the top cover 114. The drying gas then flows downwardly through a central portion of a space defined by the top cover 114. The drying gas is then exhausted out of the drying tank 110 through an exhaust port 112a formed through the fixed base 112.
The drying gas includes an isopropyl alcohol gas and a nitrogen gas. The drying gas supply unit 120 includes a first reservoir 122 for storing the nitrogen gas, a second reservoir 124 for storing the liquefied isopropyl alcohol, a first heater 126 for pre-heating the nitrogen gas, a pump 128 for pumping the liquefied isopropyl alcohol, and a second heater 130 for heating the drying gas.
The first heater 126 is connected to the first reservoir 122. The pump 128 is connected to the second reservoir 124. The second heater 130 is connected to the first heater 126 and the pump 128, respectively, through a first diverged pipe 132. The second heater 130 is also connected to the pair of nozzles 136 through a second diverged pipe 134. The nitrogen gas heated by the first heater 126 evaporates the liquefied isopropyl alcohol provided from the pump 128 in the first diverged pipe 132. The second heater 130 heats the drying gas including the isopropyl alcohol gas and the nitrogen gas. The drying gas heated by the second heater 130 is provided into the drying tank 110 through the second diverged pipe 134 and the pair of nozzles 136.
Because an inner pressure of the drying tank 110 and a supply amount of the isopropyl alcohol gas vary periodically in accordance with a moving cycle of the pump 128, drying efficiency of one of the wafers W may decrease. Also, an amount of the drying gas supplied to an upper portion Wt (e.g., wafer top) of one of the wafer Ws is less than that of the drying gas supplied to other portions of the wafer W. In addition, gas flow is unstable due to the drying gas provided from the pair of nozzles 136. As a result, defects such as water-spots are formed on a surface of the wafer W. Particularly, the defects on a central portion of the wafer W are generated more than those on other portions of the wafer W.